What’s bad about it? It gives read access to their entire server, gives access to followers-only and mentioned-only posts, not just public posts.
I don't see what I can do about Mastodon's security issue in #FediBuzz. I was hoping the Mastodon people were using the time to make permissions more fine-grained instead of sabotaging useful services that simply help supporting decentralization.
I have added relay client functionality a year ago, subscribing to many of the other public relays. However, the resulting throughput is at 0.1 posts/s which is really poor compared to the 10 posts/s we get from the public federated timelines. Implementing it was wasted time but it totally validated the client API approach. I wonder why that is still recommended by operators of big servers as they don't seem to bother joining relays at all, otherwise there would be much more traffic.
Please stop telling me "you are doing it wrong." Posing as a person who wants to control a social network has strong Elon vibes. It will make me look into Bluesky and Nostr eventually where firehose feeds are public for everyone.